介质对配合物稳定性的影响（Ⅵ）──Fe（CTS）~－NaClO_4－C_2H_

The Influence of Medium on the Stability of Coordination Compounds(Ⅵ)──The System of Fe (CTS)￣--NaClO_4-C_2H_5OH-H_2O

用分光光度法在２９３±１Ｋ温度下测定了由高价阳离子Ｆｅ^（３＋）和高价阴离子（ＣＴＳ）^（４－）（３，６－二磺酸钠－１，８－二羟基萘酚）形成配阴离子Ｆｅ（ＣＴＳ）^（－）在乙醇－水混合溶剂中的稳定常数随离子强度的变化．用推广的Ｄｅｂｙｅ－Ｈ ｃｋｅｌ方程和Ｐｉｔｚｅｒ方程计算了配位离子的热力学稳定常数，发现Ｄｅ－ｂｙｅ－Ｈ ｃｋｅｌ方程完全不能适用本体系，而基于Ｐｉｔｚｅｒ方程的多项式逼近法则可得到满意的结果。讨论了介质效应和络合反应的标准迁移自由能。

The stability of compfex anion Fe(CTS)￣-composed of cation Fe￣(3+) and anion (CTS)￣(4-)in mixed solvents of ethanol-water with weight percentage of ethanol 0, 10, 20,30,40 and 50 was measured spectrophotometrically at 293 ± 1 K by using NaClO_4 as the supporting electrolyte with ionic strength ranging from 0.1～3. 0 mol/L. The thermodynamic stability constants of Fe(CTS)￣- in various mixed solvents have been obtained by a polynomial approximation equation based on Pitzer's theory. As a comparison, the traditional De bye-H ckel equation was used to treat the same data. The results show that this polynomial approximate method is obviously superior to the Debye-H ckel equation. It was discovered that there is a linear relation between the thermodynamic stability constants of Fe(CTS)￣-and the mole fraction of organic component in mixed solvents or the reciprocal of dielectric constants of the solvents. The medium effect and the standard free energy of transfer for the coordination reaction:Fe￣(3+)+(CTS)￣(4-)=Fe(CTS)￣-is also discussed.